Notes:
A third-party library such as GnuPG is required in order to do PGP-like encryption and decryption.

(I say should, because I am not sure exactly when that note was added to the help file.)

However, as it is a third-party app that actually does the encryption/decryption it's their documentation you need to familiarize yourself with to understand the workings of the application and the valid syntax to be used. We do include examples of pre-upload and post-download commands in that SecureFX help topic.